Vehicles need transmissions in order to provide a range of speed and torque outputs necessary for vehicular travel. The task of a vehicle transmission is to convert the traction force potential of a drive engine. An automatic gearbox is a type of motor vehicle transmission that frees the driver to shift gears manually, by automatically changing/assuming gear ratios as the vehicle moves. The automatic transmission systems/automatic gear boxes are tried increasingly in the vehicle industry as it gives more freedom for the driver and hence more human friendly. There are wide ranges of such systems in practice. They may be stepped transmission systems, continuously variable transmission systems or infinitely variable transmission systems in general.
The conventional automatic gear box may consist of the following elements including but are not limited to a) torque converter b) mechanical levers c) electronic actuators d) hydraulic parts e) electronic sensors/other circuitry, specially shaped elements in addition to gears. These gear box elements deteriorate the performance/cost effectiveness of the gear box and size/simplicity in its operation. Sophisticated automatic transmission systems available in the industry perform reasonably well, but are generally cumbersome in design. These transmission systems are having exorbitant cost compared to manual transmission systems. Further, these commercially available systems call for highly skilled personnel for its maintenance. Again, they are not free from many kinds of frictional losses.
A simple planetary gear train assembly has 1) sun gear 2) planet gears 3) ring gear and 4) Carrier connecting the planet gears. For a conventional use, one of its elements among 1) sun gear, 2) ring gear and 3) Carrier are locked with any one of these, and the entire assembly functions as a high-reduction gear box. But, interestingly, if all of these three elements are not locked (constrained) with any among them, there are three degrees of freedom for a planetary gear train system, one input (i/p), one output (o/p) and one intermediate drive (i/d). The simple gear and a planetary gear train without locking any of its elements together are somewhat analogous to a NP diode and a NPN/PNP transistor respectively.
U.S. Pat. No. 8,460,143 to George Sutherland entitled “Gear-based continuously variable transmission systems and methods thereof” relates to a continuously variable transmission system including a gear set having one or more sun gears, one or more planetary gears, and a planetary gear carrier arm on which the one or more planetary gears are mounted for rotational movement. The invention provides the continuously variable transmission functionality using only passive components (planetary gears, clutches and a torque converter).
U.S. Pat. No. 5,059,163 to John W. VON Greyerz entitled “Trans-planetary mechanical torque impeller” relates to trans-planetary mechanical torque impeller having various gear ratios with no gear case attachments. It provides a torque-type propulsion through a totally mechanical, self-governing, low to high gear, trans-planetary torque impeller capable of infinitely and automatically matching the input shaft or motor power output capability to the output shaft load.
The above mentioned prior art use a torque converter in combination with special mechanical/electronic/hydraulic gadgets/sensors. Such transmission systems are a compromise of economy and performance attributes and the losses are generally high in these cases.
U.S. Pat. No. 4,682,511 to Ernest C. Wittke entitled “Gear assisted continuously variable transmission” relates to a continuously variable transmission combined with a gearshift mechanism to permit shifting of power flow under conditions of zero load and synchronous speed.
Japanese document 2013217434 to Shibata Naoyoshi entitled “continuously variable transmission” includes a differential device and synchronous torque transmission mechanism, relates to a continuously variable transmission of negative feedback by the torque disabled. The synchronous torque transmission mechanism and the transmission part are configured to work as a negative feedback mechanism such that an output torque load is fed back to always maintain input torque at a constant level.
Despite the foregoing, there is still a salient need for flexible and efficient automatic transmission system to overcome the above limitation.
Thus, the optimum design of the present invention overcomes the above mentioned problem since no elements in the gear box other than ‘rotary gears that provide better performance. This is a no loss system, when the frictional losses between gears and at bearings are not considered as the output speed of the Gear Box is maximum, for the given power of the engine and the load to the Gear Box.